We only had exactly two user reporting exactly this.
The only explanation we have, is another add-on interfering, because nowhere in the GSX code we have a check to intercept the ESC key. In fact, MSFS is different than FSX/P3D in this case, because those two would both send a "SimStart" and "SimStop" even whenever the ESC key is pressed, but MSFS doesn't so, as far as GSX is concerned, in MSFS, it has no way to know you pressed the ESC key so, the most likely reason for this seems to be some yet to be discovered add-on that is pausing the sim upon pressing ESC, for some reason.
